The Internal Mamodo (体内魔物, Tainai Mamono) are the Mamodo that guard Faudo's bloodstream. They are the equivalent of his white blood cells. There are thousands of them lurking in Faudo's body, each with the ability to spit a potent acid-like substance from their mouths. In the manga, a lot of them were sent to destroy the device that sends Faudo back to the Mamodo world and were fought through by Arth and Karudio.